1. Field of the Invention
The present invention relates to a device for measuring temperature of a semiconductor integrated circuit (hereafter xe2x80x9csemiconductor temperature measuring circuitxe2x80x9d) that measures the temperature within a semiconductor integrated circuit.
2. Description of the Related Art
The temperature within a semiconductor integrated circuit can, depending on the power consumed, rise to a high temperature of about 140xc2x0 from the environment temperature (27xc2x0 C.). Such high temperatures can alter the electrical characteristics, cause damage to the circuitry and reduce the service life of the semiconductor integrated circuit. Therefore, conventionally a semiconductor integrated circuit is provided with a temperature measuring circuit to monitor the change of temperature within the semiconductor integrated circuit.
Such a temperature measuring circuit includes two npn transistors, as a temperature measuring element, connected in series to a diode. These npn transistors are placed between a current generator provided on a power source side and the ground. The temperature measuring circuit outputs a voltage corresponding to the temperature within the semiconductor integrated device from the collector terminals of the npn transistors.
However, in this temperature measuring circuit, the voltage output depends greatly on the temperature characteristics of the npn transistors. This makes the setting of the temperature at 0V output to any preferred value or setting of a temperature in order to obtain a desired temperature voltage characteristics difficult.
Further, as the temperature characteristics of the npn transistors are altered in order to measure the temperature, it is difficult to change the temperature voltage characteristics gradient to any desired value, moreover, it exerts a bad effect on electric characteristics of other circuit elements in the semiconductor integrated device.
It is an objective of the present invention to solve the problems in the conventional technology.
The semiconductor temperature measuring circuit according to one aspect of the present invention comprises a first current mirror circuit and a second current mirror circuit both connected to a positive power source, each of the first current mirror circuit and the second mirror circuit having a control electrode, the control electrodes of the first current mirror circuit and the second mirror circuit are commonly connected, the second current mirror circuit having a first output terminal and a second output terminal; a third current mirror circuit provided between an output terminal of the first current mirror circuit and the ground, the third current mirror circuit being made of a first npn transistor having a first emitter size and a second npn transistor having a second emitter size, the first emitter size being greater than the second emitter size, an emitter electrode of the first npn transistor is connected to the ground via a first resistor, and an emitter electrode of the second npn transistor is directly connected to the ground; a third npn transistor having a collector electrode connected to the first output terminal of the second current mirror circuit and an emitter electrode connected to the negative power source, and a base electrode connected to the negative power source via a second resistor; an N channel transistor having a control electrode, a first signal electrode, and a second signal electrode, wherein the control electrode is connected to the first output terminal of the second current mirror circuit, the first signal electrode is connected to the second output terminal of the second current mirror circuit, and the second signal electrode is connected to the base electrode of the third npn transistor; and an operational amplifier that has a negative gradient with respect to temperature, the operational amplifier having a negative input terminal and a positive input terminal, the negative input terminal is connected to a node between the second output terminal of the second current mirror circuit and the first signal electrode of the N channel transistor, as well as to an output terminal via a resistor unit, and the positive input phase terminal is directly connected to the ground.
The semiconductor temperature measuring circuit according to another aspect of the present invention comprises the first current mirror circuit and the second current mirror circuit; the third current mirror circuit; the third npn transistor; and the N-channel transistor described above. In addition the semiconductor temperature measuring circuit has an operational amplifier that has a positive gradient with respect to temperature, the operational amplifier having a positive input terminal and a negative input terminal, the positive input terminal is connected to a node between the second output terminal of the second current mirror circuit and the first signal electrode of the N channel transistor, as well as to the ground via a resistor unit, and the negative input phase terminal is directly connected to the output terminal.
These and other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings.